Torsional damping for gas turbine engines

ABSTRACT

The present disclosure is directed to a gas turbine engine assembly having a compressor configured to increase pressure of incoming air, a combustion chamber, at least one turbine coupled to a generator, a torsional damper, and a controller. The combustion chamber is configured to receive a pressurized air stream from the compressor. Further, fuel is injected into the pressurized air in the combustion chamber and ignited so as to raise a temperature and energy level of the pressurized air. The turbine is operatively coupled to the combustion chamber so as to receive combustion products that flow from the combustion chamber. The generator is coupled to the turbine via a shaft. Thus, the torsional damper is configured to dampen torsional oscillations of the generator. Moreover, the controller is configured to provide additional damping control to the generator.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 15/491,638, filed on Apr. 19, 2017, which is a divisionalapplication of U.S. patent application Ser. No. 14/920,993, filed onOct. 23, 2015, the disclosures of each are incorporated by referenceherein in their entireties.

FIELD OF THE INVENTION

The present application relates generally to gas turbine engines andmore particularly to a torsional damper and torsional damping control toprotect gas turbine engines from torsional interaction.

BACKGROUND OF THE INVENTION

A gas turbine engine generally includes, in serial flow order, acompressor section, a combustion section, a turbine section, and anexhaust section. In operation, air enters an inlet of the compressorsection where one or more axial compressors progressively compress theair until it reaches the combustion section. Fuel is mixed with thecompressed air and burned within the combustion section to providecombustion gases. The combustion gases are routed from the combustionsection through a hot gas path defined within the turbine section andthen exhausted from the turbine section via the exhaust section.

In particular configurations, the turbine section includes, in serialflow order, a high pressure (HP) turbine and a low pressure (LP)turbine. The HP turbine and the LP turbine each include variousrotatable turbine components such as turbine rotor blades, rotor disksand retainers, and various stationary turbine components such as statorvanes or nozzles, turbine shrouds and engine frames. The rotatable andthe stationary turbine components at least partially define the hot gaspath through the turbine section. As the combustion gases flow throughthe hot gas path, thermal energy is transferred from the combustiongases to the rotatable turbine components and the stationary turbinecomponents.

Gas turbine engines and other types of turbo-machinery are often used todrive loads such as electrical generators. Gas turbine engines and otherlarge drive train systems have a moment of inertia, a torsionalstiffness, and natural damping. The low mechanical damping in high powertrains can cause torsional interaction between power system componentsand the mechanical drive train. For example, if one of the naturalfrequencies of the mechanical drive train is excited to a torsionalresonance, the resulting alternating mechanical torque can reach valuesthat can damage or cause fatigue in components of the rotor shaftsystem.

Thus, a system and method of operating a gas turbine engine or similarmachinery so as to provide improved torsional damping would be welcomedin the art.

BRIEF DESCRIPTION OF THE INVENTION

Aspects and advantages of the invention will be set forth in part in thefollowing description, or may be obvious from the description, or may belearned through practice of the invention.

In accordance with one aspect of the present disclosure, a gas turbineengine assembly is disclosed. The gas turbine engine assembly includes acompressor configured to increase pressure of incoming air, a combustionchamber, at least one turbine (e.g. high- and low-pressure turbines)coupled to a generator, a torsional damper, and a controller. Thecombustion chamber is configured to receive a pressurized air streamfrom the compressor. Further, fuel is injected into the pressurized airin the combustion chamber and ignited so as to raise a temperature andenergy level of the pressurized air. The turbine is operatively coupledto the combustion chamber so as to receive combustion products that flowfrom the combustion chamber. The generator is coupled to a shaft systemof the turbine (e.g. any one of or combination of a high pressure shaftsystem, a low pressure shaft system, or an intermediate shaft system)via a shaft. Thus, the torsional damper is configured to dampentorsional oscillations on the shaft system of the generator, e.g. causedby negative damping and/or forced excitations. Moreover, the controlleris configured to provide additional damping control to the generator.

In one embodiment, the torsional damper may include at least one of amechanical damper or an electrical damper. For example, in particularembodiments, the mechanical damper may include a viscous damper. Morespecifically, the viscous damper may be positioned circumferentiallyaround the shaft of the generator.

In certain embodiments, the gas turbine engine assembly may also includea power converter having one or more electrical circuits. Thus, in suchembodiments, the electrical damper may include a resistor integratedinto one of the electrical circuits of the power converter. In addition,in certain embodiments, the controller may be configured to control theresistor so as to prohibit the generator from having a constant powerload at frequencies of torsional interaction.

In another embodiment, the gas turbine engine assembly may include apower bus damper configured to prohibit the generator from having aconstant power load at frequencies of torsional interaction. Morespecifically, in certain embodiments, the power bus damper may includeat least one of an active load, a controlled resistive load, an energystorage device, or similar.

In further embodiments, the controller may be configured to control apower factor of the generator so as to provide torsional damping of thegenerator by decreasing the power factor and creating losses internal towindings of the generator.

In additional embodiments, the torsional damper may be configured toreduce the oscillating torque between the generator and the turbine.

In another aspect, the present disclosure is directed to an electricalpower system. The electrical power system includes a first inertiasystem connected to a second inertia system via a shaft. Further, thefirst inertia system is larger than the second inertia system. Inaddition, the second inertia system may include a negative ratio ofdelta torque and delta speed. Thus, the electrical power system alsoincludes a torsional damper configured to dampen torsional oscillationsbetween the first and second inertia systems, e.g. caused by negativedamping and/or forced excitations.

In yet another aspect, the present disclosure is directed to a method ofoperating a gas turbine engine assembly. The method includespressurizing air via a compressor of the assembly. The method alsoincludes providing the pressurized air from the compressor to acombustion chamber. Still another step includes injecting fuel into thepressurized air within the combustion chamber and igniting the fuel soas to raise a temperature and energy level of the pressurized air. Themethod further includes providing combustion products from thecombustion chamber to a turbine coupled to a generator of the assembly.In addition, the method includes damping torsional oscillations of ashaft system of the generator via a torsional damper and additionaldamping provided by a generator controller.

In one embodiment, the step of damping torsional oscillations of theshaft system of the generator via the torsional damper may furtherinclude providing at least one of a mechanical damper or an electricaldamper. More specifically, in certain embodiments, the step of dampingtorsional oscillations of the shaft system of the generator may includepositioning the mechanical damper circumferentially around the shaft.

In another embodiment, the method may include integrating the electricaldamper into a power converter of the generator. More specifically, insuch an embodiment, the electrical damper may include a resistor. Forexample, in certain embodiments, the method may include controlling, viathe controller, the resistor so as to prohibit the generator from havinga constant power load at frequencies of torsional interaction.

In additional embodiments, the method may include operatively coupling apower bus damper with the power converter and controlling the power busdamper so as to prohibit the generator from having a constant powerload. More specifically, in such embodiments, the power bus damper mayinclude at least one of an active load, a controlled resistive load, anenergy storage device, or similar.

In yet another embodiment, the method may include controlling a powerfactor of the generator so as to provide torsional damping of thegenerator by decreasing the power factor and creating losses internal towindings of the generator.

These and other features, aspects and advantages of the presentinvention will become better understood with reference to the followingdescription and appended claims. The accompanying drawings, which areincorporated in and constitute a part of this specification, illustrateembodiments of the invention and, together with the description, serveto explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth in the specification, which makes reference to the appendedfigures, in which:

FIG. 1 illustrates a schematic cross-sectional view of a gas turbineengine according to the present disclosure;

FIG. 2 illustrates a block diagram of one embodiment of a gas turbineengine assembly according to the present disclosure;

FIG. 3 illustrates a block diagram of another embodiment of a gasturbine engine assembly according to the present disclosure;

FIG. 4 illustrates a block diagram of yet another embodiment of a gasturbine engine assembly according to the present disclosure;

FIG. 5 illustrates a block diagram of one embodiment of a generator of agas turbine engine assembly according to the present disclosure;

FIG. 6 illustrates a block diagram of another embodiment of a gasturbine engine assembly according to the present disclosure;

FIG. 7 illustrates a partial block diagram of one embodiment of agenerator and a power converter of a gas turbine engine assemblyaccording to the present disclosure;

FIG. 8 illustrates a block diagram of one embodiment of an electricaldamper of a gas turbine engine assembly according to the presentdisclosure;

FIG. 9 illustrates a partial block diagram of another embodiment of agas turbine engine assembly according to the present disclosure,particularly illustrating various embodiments of a power bus damper;

FIG. 10 illustrates a block diagram of one embodiment of an electricalpower system according to the present disclosure; and

FIG. 11 illustrates a flow diagram of one embodiment of a method ofoperating a gas turbine engine assembly according to the presentdisclosure.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to present embodiments of theinvention, one or more examples of which are illustrated in theaccompanying drawings. The detailed description uses numerical andletter designations to refer to features in the drawings. Like orsimilar designations in the drawings and description have been used torefer to like or similar parts of the invention. As used herein, theterms “first”, “second”, and “third” may be used interchangeably todistinguish one component from another and are not intended to signifylocation or importance of the individual components. The terms“upstream” and “downstream” refer to the relative flow direction withrespect to fluid flow in a fluid pathway. For example, “upstream” refersto the flow direction from which the fluid flows, and “downstream”refers to the flow direction to which the fluid flows.

Further, as used herein, the terms “axial” or “axially” refer to adimension along a longitudinal axis of an engine. The term “forward”used in conjunction with “axial” or “axially” refers to a directiontoward the engine inlet, or a component being relatively closer to theengine inlet as compared to another component. The term “rear” used inconjunction with “axial” or “axially” refers to a direction toward theengine nozzle, or a component being relatively closer to the enginenozzle as compared to another component. The terms “radial” or“radially” refer to a dimension extending between a center longitudinalaxis of the engine and an outer engine circumference.

Generally, the present disclosure is directed to a gas turbine engineassembly having improved torsional damping. The gas turbine engineassembly generally includes a compressor, a combustion chamber, at leastone turbine (e.g. a high- and low-pressure turbine) coupled to agenerator, a torsional damper, and a controller configured to provideadditional damping. As is generally understood, the combustion chamberis configured to receive pressurized air from the compressor, whereinfuel is injected into the pressurized air and ignited so as to raise atemperature and energy level of the pressurized air. The turbine isoperatively coupled to the combustion chamber so as to receivecombustion products that flow from the combustion chamber. The generatoris coupled to a shaft system of the turbine via a shaft. Thus, thetorsional damper (i.e. mechanical, electrical, and/or both) isconfigured to dampen torsional oscillations of the shaft system of thegenerator. In addition, the controller is configured to provideadditional damping control to the generator.

Thus, the present disclosure provides many advantages not present in theprior art. For example, the present disclosure provides a stablemechanical drive of a generator or motor for an aircraft power system aswell as any other suitable electrical power system by reducingoscillating torque between the generator to the turbine (i.e. caused bynegative damping and/or forced excitations). In addition, the systemprovides simpler analysis of the power system loads. Further, thetorsional damping of the present disclosure is configured to smooth thetransmission of torque to the turbine, thereby allowing overall turbinedesign requirements to be relaxed. Thus, the size, cost, and/or weightof the turbine thus may be reduced. Moreover, the gas turbine engine maybe more reliable with longer component lifetime. In addition, thetorsional damping features of the present disclosure may be originalequipment or part of a retrofit.

Referring now to the drawings in detail, wherein identical numeralsindicate the same elements throughout the figures, FIG. 1 illustrates anexemplary gas turbine engine 10 (high bypass type) according to oneembodiment of the present disclosure. As shown, the illustrated gasturbine engine 10 has an axial longitudinal centerline axis 12therethrough for reference purposes. Further, the gas turbine engine 10preferably includes a core gas turbine engine generally identified bynumeral 14 and a fan section 16 positioned upstream thereof. The coreengine 14 typically includes a generally tubular outer casing 18 thatdefines an annular inlet 20. The outer casing 18 further encloses andsupports a booster 22 for raising the pressure of the air that enterscore engine 14 to a first pressure level. A high pressure, multi-stage,axial-flow compressor 24 receives pressurized air from the booster 22and further increases the pressure of the air. The pressurized air flowsto a combustor 26, where fuel is injected into the pressurized airstream and ignited to raise the temperature and energy level of thepressurized air. The high energy combustion products flow from thecombustor 26 to a first (high pressure) turbine 28 for driving the highpressure compressor 24 through a first (high pressure) drive shaft 30,and then to a second (low pressure) turbine 32 for driving the booster22 and the fan section 16 through a second (low pressure) drive shaft 34that is coaxial with the first drive shaft 30. After driving each of theturbines 28 and 32, the combustion products leave the core engine 14through an exhaust nozzle 36 to provide at least a portion of the jetpropulsive thrust of the engine 10.

The fan section 16 includes a rotatable, axial-flow fan rotor 38 that issurrounded by an annular fan casing 40. It will be appreciated that fancasing 40 is supported from the core engine 14 by a plurality ofsubstantially radially-extending, circumferentially-spaced outlet guidevanes 42. In this way, the fan casing 40 encloses the fan rotor 38 andthe fan rotor blades 44. The downstream section 46 of the fan casing 40extends over an outer portion of the core engine 14 to define asecondary, or bypass, airflow conduit 48 that provides additional jetpropulsive thrust.

From a flow standpoint, it will be appreciated that an initial airflow,represented by arrow 50, enters the gas turbine engine 10 through aninlet 52 to the fan casing 40. The airflow passes through the fan blades44 and splits into a first air flow (represented by arrow 54) that movesthrough the conduit 48 and a second air flow (represented by arrow 56)which enters the booster 22.

The pressure of the second airflow 56 is increased and enters the highpressure compressor 24, as represented by arrow 58. After mixing withfuel and being combusted in the combustor 26, the combustion products 60exit the combustor 26 and flow through the first turbine 28. Thecombustion products 60 then flow through the second turbine 32 and exitthe exhaust nozzle 36 to provide at least a portion of the thrust forthe gas turbine engine 10.

Still referring to FIG. 1 , the combustor 26 includes an annularcombustion chamber 62 that is coaxial with longitudinal centerline axis12, as well as an inlet 64 and an outlet 66. As noted above, thecombustor 26 receives an annular stream of pressurized air from a highpressure compressor discharge outlet 69. A portion of this compressordischarge air (“CDP” air) flows into a mixer (not shown). Fuel isinjected from a fuel nozzle 100 to mix with the air and form a fuel-airmixture that is provided to the combustion chamber 62 for combustion.Ignition of the fuel-air mixture is accomplished by a suitable igniter,and the resulting combustion gases 60 flow in an axial direction towardand into an annular, first stage turbine nozzle 72. The nozzle 72 isdefined by an annular flow channel that includes a plurality ofradially-extending, circumferentially-spaced nozzle vanes 74 that turnthe gases so that they flow angularly and impinge upon the first stageturbine blades of the first turbine 28. As shown in FIG. 1 , the firstturbine 28 preferably rotates the high-pressure compressor 24 via thefirst drive shaft 30. The low-pressure turbine 32 preferably drives thebooster 24 and the fan rotor 38 via the second drive shaft 34.

The combustion chamber 62 is housed within engine outer casing 18. Fuelis supplied into the combustion chamber by one or more fuel nozzles.Liquid fuel is transported through conduits or passageways within a stemof each fuel nozzle. Further, the gas turbine engine 10 may use naturalgas, various types of syngas, and/or other types of fuels. Moreover, thegas turbine engine 10 may have different configurations and may useother types of components in addition to those components shown.Multiple gas turbine engines, other types of turbines, and other typesof power generation equipment also may be used herein together.

Referring now to FIGS. 2-4 , various simplified, schematic views of agas turbine engine assembly 100 according to the present disclosure isillustrated. As shown in the illustrated embodiments, the gas turbineengine assembly 100 generally includes a compressor 102, a combustionchamber 104, a high-pressure turbine 106 and a high-pressure shaft 110,a low-pressure turbine 108 and a low-pressure shaft 112, and variousother optional components. For example, the gas turbine engine assembly100 may also include a generator 114 or a similar type of load. Thegenerator 114 may be any type of device for the generation of electricalpower. More specifically, as shown in FIG. 5 , the generator 114 mayinclude a generator rotor 113 that rotates within a generator stator115. More specifically, rotation of the rotor 113 is due to theinteraction 13 between the windings and/or magnetic fields of thegenerator 114 which produces a torque around the rotor's axis. Further,the generator 114 may be driven by the turbines 106, 108 via the shafts110, 112. Other components and other configurations may also be usedaccording to the present disclosure.

In addition, as shown in FIGS. 6 and 7 , the gas turbine engine assembly100 may also include a power converter 122 having one or electricalcircuits 127. The power converter 122 may include any suitable powerconverter. For example, the power converter 122 generally includescircuitry for converting a variable frequency AC voltage from thegenerator 114 into a voltage that is supplied to power grid (not shown).Specifically, the power converter 122 is selectively activated toproduce an output voltage, which is the AC voltage supplied to powergrid. Thus, the power converter 122 may include various power switchingdevices such as, for example, insulated gate bipolar transistors(IGBTs), integrated gate-commutated thyristors (IGCTs), or any othersuitable switching devices.

Referring now to FIGS. 2-9 , the gas turbine engine assembly 100 alsomay include a torsional damper 116 configured to dampen torsionaloscillations of the generator 114 and/or a controller 120 configured toprovide additional damping control to the engine 10. Thus, in certainembodiments, the torsional damper 116 is configured to reduce theoscillating torque between the generator 114 and the turbine 106, 108.

More specifically, as shown in the illustrated embodiment of FIGS. 2-5 ,the torsional damper 116 may be a mechanical damper 117. In addition, asshown, the mechanical damper 117 may be positioned circumferentiallyaround the shaft 118, which operatively couples the low-pressure turbine108 to the generator 114. Further, as shown in FIG. 2 , the mechanicaldamper 117 may be configured at the front end of the generator 114.Alternatively, as shown in FIG. 3 , the mechanical damper 117 may beconfigured at the rear end of the generator 114. In addition, themechanical damper 117 may be separate from the generator 114 (FIG. 2 )or integral with the generator 114 (FIG. 5 ). Further, as shown in FIG.2 , the torsional damper 116 and the generator 114 may be mechanicallyconnected to the low-pressure shaft system (i.e. the fan, booster,and/or low-pressure turbine 108). Alternatively, as shown in FIG. 4 ,the torsional damper 116 and the generator 114 may be mechanicallyconnected to the high-pressure shaft system (i.e. the compressor 102and/or the high-pressure turbine 106). In still additional embodiments,the torsional damper 116 may be connected to any other shaft system.

It should be understood that the mechanical damper 117 may be anysuitable mechanical damper now known or later developed in the art. Forexample, in one embodiment, the mechanical damper 117 may include aviscous damper. As used herein, a viscous damper generally refers to amechanical device, which resists motion via viscous friction. Theresulting force is substantially proportional to the oscillatingvelocity, but acts in the opposite direction, thereby decreasing theoscillation and absorbing energy without resulting in steady statelosses.

It should also be understood that, in addition to or in placement of themechanical damper 117, additional damping means may be used in theengine 10. For example, as shown in FIGS. 6-8 , the torsional damper 116may include an electrical damper 124. More specifically, as shown, theelectrical damper 124 may be integrated into the power converter 122 ofthe assembly 100. In certain embodiments, as shown in FIGS. 7 and 8 ,the electrical damper 124 may include one or more resistors 125integrated into one of the electrical circuits 127 of the powerconverter 122. Thus, in such an embodiment, the controller 120 may alsobe configured to control the resistor 125 so as to prohibit thegenerator 114 from having a constant power load, thereby providingtorsional damping thereof. Accordingly, the electrical damper 124 isconfigured to provide damping for forced excitations introduced to theassembly 100.

In another embodiment, as shown in FIG. 9 , the gas turbine engineassembly 100 may include a power bus damper component 126 configured toprohibit the generator 114 from having a constant power load. Morespecifically, as shown, the power bus damper component 126 may includeat least one of an active load 128, a controlled resistive load 130, abus damper 132, or an energy storage device 134 (e.g. a battery,capacitor, or similar). Further, as shown, the power bus dampercomponent(s) 126 is configured to receive a speed and/or torque signal136 from the generator 114 or the controller 120. Based on the signal136, the bus damper component 126 is configured to prevent the bus fromhaving a constant power load separated from voltage control. Further,for generators having a power converter (as shown), the power factor canbe reduced to increase generator losses at the required mechanicaldamping frequencies. Such operation does not result in steady statelosses, but rather only losses required to damp torsional oscillations.

In further embodiments, the controller 120 is configured to control apower factor of the generator 114 so as to provide torsional damping ofthe generator 114, e.g. by decreasing the power factor and creatinglosses internal to windings of the generator 114 and connecting cables.

Referring now to FIG. 10 , it should be understood that the advantagesdescribed above may also be suitable for additional power systems, inaddition to the gas turbine engine 10 of an aircraft power system asdescribed herein. For example, additional electrical power systems thatmay utilize the torsional damping features of the present disclosure mayinclude gas turbine engines, wind turbines, steam turbines, or any othersuitable generator-driven system. For example, as shown in FIG. 10 , aschematic diagram of an electrical power system 150 having improvedtorsional damping according to the present disclosure is illustrated.More specifically, as shown, the electrical power system 150 includes afirst inertia system 152 connected to a second inertia system 154 via ashaft 156. Further, as shown, the first inertia system 152 is largerthan the second inertia system 154. For example, in certain embodiments,the first inertia system 152 may be a generator, whereas the secondinertia system 154 may include a generator driver, including but notlimited to a low-pressure shaft system, a high-pressure shaft system, anintermediate shaft system, one or more rotor blades (optionally coupledto a gearbox), or any other suitable generator-driving component.

Thus, the electrical power system 150 may include a torsional damper 158configured to dampen torsional oscillations between the first and secondinertia systems 152, 154. In such systems, the second inertia system 154may have a negative ratio of delta torque and delta speed, i.e. may havenegative damping. Thus, the torsional damper 158 may be configured tocorrect the negative damping of the second inertia system 154.Alternatively, the torsional damper 158 may be configured to providedamping for forced excitations introduced to the systems 152, 154.

In additional embodiments, the electrical power system 150 includes acontroller 160 configured to provide additional damping control for thefirst and second inertia systems 152, 154. Referring now to FIG. 11 , aflow diagram of one embodiment of a method 200 of operating a gasturbine engine. As shown at 202, the method 200 includes pressurizingair via a compressor 24 of the gas turbine engine 10. As shown at 204,the method 200 includes providing the pressurized air to a combustionchamber 62 from the compressor 24. As shown at 206, the method 200includes injecting fuel into pressurized air within the combustionchamber 62 and igniting the fuel so as to raise a temperature and energylevel of the pressurized air. As shown at 208, the method 200 includesproviding combustion products from the combustion chamber 62 to theturbine (e.g. turbines 106, 108) coupled to a generator 114. As shown at210, the method 200 also includes damping torsional oscillations of thegenerator 114 via a torsional damper 116 and additional damping providedby a generator controller 120.

In one embodiment, the step of damping torsional oscillations of thegenerator 114 via the torsional damper 116 may further include providingat least one of a mechanical damper 117 or an electrical damper 124.More specifically, in certain embodiments, the step of damping torsionaloscillations of the generator 114 via the torsional damper 116 mayinclude positioning the mechanical damper 117 circumferentially aroundthe shaft 118 (FIG. 2 ).

In another embodiment, as shown in FIG. 7 , the method 200 may includeintegrating the electrical damper 124 into the power converter 122. Morespecifically, as mentioned, the electrical damper 124 may include aresistor 125. Thus, in such embodiments, the method 200 may includecontrolling, via the controller 120, the resistor 125 so as to prohibitthe generator 114 from having a constant power load at frequencies oftorsional interaction.

In additional embodiments, the method 200 may include operativelycoupling a power bus damper 126 with the power converter 122 and/or thecontroller 120. Thus, the power bus damper 126 is configured to prohibitthe generator 114 from having a constant power load. More specifically,as described herein, the power bus damper 126 may include an active load128, a controlled resistive load 130, a bus damper 132, an energystorage device 134, or similar, or combinations thereof.

In yet another embodiment, the method 200 may include controlling apower factor of the generator 114 so as to provide torsional damping ofthe generator 114, e.g. by decreasing the power factor and creatinglosses internal to windings of the generator 114 or connecting cables.

It should also be understood that although the use of the gas turbineengine assembly 100 has been described herein, the torsional damper 160may be used with any type of turbo-machinery and the like. Thus, thecombination of any or all of the damping components and/or featuresdescribed herein can be used to provide positive generator damping, e.g.at specific frequencies, wide frequency ranges, and may be adjustable.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they include structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

1-11. (canceled)
 12. A method of operating a gas turbine engineassembly, comprising: providing combustion products from a combustionchamber to a turbine coupled to a generator; and damping torsionaloscillations of a shaft system of the generator via a controllerproviding a speed signal or a torque signal to at least one of a batteryor a load to prohibit the generator from having a constant power load atfrequencies of torsional interaction.
 13. The method of claim 12,further comprising: damping torsional oscillations of the shaft systemof the generator via a mechanical damper.
 14. The method of claim 12,wherein the controller controls a power bus damper to prohibit thegenerator from having a constant power load at the frequencies oftorsional interaction.
 15. The method of claim 12, wherein the power busdamper comprises at least one of an active load, a controlled resistiveload, or an energy storage device.
 16. The method of claim 15, whereinthe power bus damper is further configured to prevent a bus from havinga constant power load on the generator at the frequencies of torsionalinteractions separated from voltage control.
 17. The method of claim 12,further comprising: converting, via a power converter operably coupledwith the controller, AC voltage into DC voltage, wherein the powerconverter is configured to dampen torsional oscillations by reducing apower factor to increase generator losses at mechanical dampingfrequencies.
 18. The method of claim 12, wherein the controller controlsa controlled resistive load of a resistor to prohibit the generator fromhaving a constant power load at frequencies of torsional interaction.19. The method of claim 18, wherein the controlled resistive load isvaried to prohibit the generator from having a constant power load. 20.The method of claim 12, further comprising: pressurizing air via acompressor of the gas turbine engine assembly.
 21. The method of claim20, further comprising: providing the pressurized air from thecompressor to a combustion chamber.
 22. The method of claim 21, furthercomprising: injecting fuel into the pressurized air within thecombustion chamber and igniting the fuel to raise a temperature andenergy level of the pressurized air.
 23. A method of operating a gasturbine engine assembly, comprising: providing combustion products froma combustion chamber to a turbine coupled to a generator; andcontrolling, via a controller, a power bus damper to dampen torsionaloscillations of a shaft system of the generator via providing a speedsignal or a torque signal to at least one of a battery or a load toprohibit the generator from having a constant power load at frequenciesof torsional interaction.
 24. The method of claim 23, furthercomprising: damping torsional oscillations of the shaft system of thegenerator via a mechanical damper.
 25. The method of claim 23, whereinthe power bus damper comprises at least one of an active load, acontrolled resistive load, or an energy storage device.
 26. The methodof claim 25, wherein the power bus damper is further configured toprevent a bus from having a constant power load on the generator at thefrequencies of torsional interactions separated from voltage control.27. The method of claim 23, further comprising: converting, via a powerconverter operably coupled with the controller, AC voltage into DCvoltage, wherein the power converter is configured to dampen torsionaloscillations by reducing a power factor to increase generator losses atmechanical damping frequencies.
 28. The method of claim 23, wherein thecontroller controls a controlled resistive load of a resistor toprohibit the generator from having a constant power load at frequenciesof torsional interaction.
 29. A method of operating a gas turbine engineassembly, comprising: providing combustion products from a combustionchamber to a turbine coupled to a generator; and damping torsionaloscillations of a shaft system of the generator via a controllerproviding a speed signal or a torque signal to at least one of a batteryor a load to prohibit the generator from having a constant power load atfrequencies of torsional interaction; and converting, via a powerconverter operably coupled with the controller, AC voltage into DCvoltage, wherein the power converter is configured to dampen torsionaloscillations by reducing a power factor to increase generator losses atmechanical damping frequencies.
 30. The method of claim 29, wherein thecontroller controls a controlled resistive load of a resistor toprohibit the generator from having a constant power load at frequenciesof torsional interaction.
 31. The method of claim 30, wherein thecontrolled resistive load is varied to prohibit the generator fromhaving a constant power load.